When drilling a well, a downhole motor is used to provide a rotational force to a drill bit via a rotating drive shaft, also called a mandrel. The mandrel is rotated within a bearing housing. The rotation of the mandrel relative to the bearing housing can create significant amounts of friction, which can quickly wear down components, and can cause deformation, overheating, and other types of damage.
Bearing assemblies have been developed to compensate for these difficulties, conventional bearing assemblies being usable to resist and withstand the friction created when a central shaft rotates within a housing. Prior techniques and assemblies include use of a coating process about the mandrel and inner diameter of the housing, use of carbide inserts, and use of standard roller and ball bearings. Prior coating techniques include various means for applying a facing surface to a bearing, such as welding, spraying, plating, or various manual techniques.
Prior coating processes generally include adhesion and fusion processes. Fusion is typically more reliable than adhesion due to the fact that when fusion is used, a coating material is melted partially into the carrier metal to form a superior bond. Use of fusion normally requires a significant amount of heat, in excess of 800 or 900 degrees Fahrenheit, to melt the surface of materials, which can often disadvantageously affect the metallurgical properties of the bearing housing, mandrel, and other components subjected to the high temperatures. In addition, extreme heat can dilute the fused material into the substrate, causing undesired intermingling and creating an unsuitable coating.
Further, fusion processes require large apparatuses for application of material and for heating, causing the performance of fusion operations to be impossible within restricted spaces, such as surfaces within an assembled bearing housing.
As a result, conventional bearings often have a first hard facing surface disposed over a mandrel, formed using a fusion process, while a second opposing hard facing surface disposed along the inner surface of the bearing housing is formed using a differing material and/or a differing process. Often, the exterior hard facing surface along a housing member is worn out more quickly than the interior hard facing surface along a drive shaft, limiting the useful life of a conventional radial bearing to about 300 operating hours, requiring frequent costly and time consuming replacement.
Attempts to overcome this difficulty have typically focused on the types of materials used to form bearing surfaces, however attempted improvements to bearings and wear resistant surfaces have resulted in only negligible increases in the operational life of these surfaces due to the difficulties inherent in forming a fused hard facing surface along the interior of a housing.
Other prior attempts to overcome these difficulties have included use of a “dummy” tubular sleeve, over which interior facing materials and an external layer can be applied and fused together, using the same process and materials. The tubular sleeve can then be machined and/or ground away, so that only the interior facing layer and the external layer remain. The resulting product can then be installed over a mandrel within a bearing housing, however use and destruction of an additional tubular sleeve is a time-consuming and costly process.
A need exists for a method for producing a radial bearing or similar wear resistant surface, the method being usable within a bearing housing, thereby eliminating the need for a “dummy” tubular sleeve and related manufacturing steps, such as shrink-fitting components to engage the tubular sleeve, thereby significantly reducing the time and cost required for manufacture of the radial bearing or wear resistant surface. Additionally, the production of a wear resistant surface within a bearing housing, eliminating the need for bulky inserts, would conserve space within the housing, enabling a mandrel having a greater diameter to be installed for accommodating high torque and/or side loading applications.
A further need exists for a method for producing a radial bearing or similar wear resistant surface using fusion to associate an interior facing layer with an external layer, providing a radial bearing capable of high side load applications and a useful life of 1200 to 1500 operating hours, or more, as compared to a useful life of 300 operating hours for a conventional radial bearing or wear resistant surface.
A need also exists for a method for producing a radial bearing or similar wear resistant surface having opposing hard facing layers using comparatively low energy, which maintains the temperature of the bearing housing and other components as low as 400 degrees Fahrenheit, or less, to avoid changing the metallurgical properties of the components.
The present embodiments meet these needs.